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fix(security): harden analytics Basic Auth (fail-closed + constant-time) #261

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fix(security): harden analytics Basic Auth (fail-closed + constant-time) #261

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19 changes: 18 additions & 1 deletion server/routes/analytics.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ package routes

import (
"context"
"crypto/subtle"
"fmt"
"net/http"
"os"
Expand All @@ -12,6 +13,7 @@ import (
"github.com/gin-gonic/gin"
"go.mongodb.org/mongo-driver/bson"
"schej.it/server/db"
"schej.it/server/logger"
"schej.it/server/models"
"schej.it/server/slackbot"
)
Expand All @@ -21,9 +23,24 @@ func AnalyticsBasicAuth() gin.HandlerFunc {
return func(c *gin.Context) {
analyticsUsername := os.Getenv("ANALYTICS_USERNAME")
analyticsPassword := os.Getenv("ANALYTICS_PASSWORD")

// Fail closed if credentials aren't configured. Otherwise empty env
// vars combined with the old `user != "" || pass != ""` style check
// would let a request with empty credentials authenticate, exposing
// these admin endpoints (user lookup, manual upgrade/downgrade).
if analyticsUsername == "" || analyticsPassword == "" {
logger.StdErr.Println("ANALYTICS_USERNAME/ANALYTICS_PASSWORD not configured; refusing analytics request")
c.AbortWithStatusJSON(http.StatusServiceUnavailable, gin.H{"error": "Analytics auth not configured"})
return
}

user, pass, hasAuth := c.Request.BasicAuth()

if !hasAuth || user != analyticsUsername || pass != analyticsPassword {
// Constant-time comparison to avoid leaking the credentials via timing.
userMatch := subtle.ConstantTimeCompare([]byte(user), []byte(analyticsUsername)) == 1
passMatch := subtle.ConstantTimeCompare([]byte(pass), []byte(analyticsPassword)) == 1

if !hasAuth || !userMatch || !passMatch {
c.Header("WWW-Authenticate", `Basic realm="Restricted"`)
c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "Unauthorized"})
return
Expand Down